180 VENERIDZ. 
SuBFAMILY DOSINIINA. 
Shell orbicular, mostly flattened and concentrically striate ; 
pallial sinus oblique, triangular. Siphons united; foot subquad- 
rangular, without byssiferous furrow. 
Dosinta, Scopoli, 1777. 
Syn.—Artemis, Poli, 1791. Orbiculus, Muhlf.,1811. Exoleta, 
Brown. Asa, Leach. 
Distr.—100 sp.  Boreal—Tropical seas; low-water—80 
fathoms. Fossil, 13 sp. Cret.—; United States, Europe, South 
India. D. discus, Reeve (exiv, 32). 
Shell orbicular, compressed, concentrically striated, pale, 
ligament sunk; lunule deep; hinge like Cytherea; margins 
even ; pallial sinus deep, angular, ascending. 
Animal with a large hatchet-shaped foot, projecting from the 
ventral margin of the shell; mantle-margins slightly plaited ; 
siphons united to their ends; orifices simple, palpi narrow. 
Gemma, Deshayes. 
Syn.—Tottenia, Perkins, 1869. 
Distr.—U. 8. G. gemma, Totten (exiii, 29). 
Shell rounded, subtriangular, subequilateral, smooth, margins 
crenulated within; hinge short and narrow; three teeth in the 
left valve, the middle one conical, arcuated; two divergent 
teeth and an intermediate pit in the right valve; pallial impres- 
sion marginal, with a narrow deep sinus. 
The species of this genus are very small, not exceeding 3°5 
mill. in diameter. 
CyYpRIMERIA, Conrad, 1864. 
Distr.—Cretaceous ; North America, Europe. C. discus, 
Matheron (cxv, 39, 40, 42). 
Shell lentiform; hinge of right valve broad, with a bifid 
oblique cardinal tooth and two oblique acute anterior teeth, 
with an intermediate pit for the reception of the tooth in the 
opposite valve. 
Cyrcniina, Deshayes. 
Distr.—l10 sp. Senegal, India, China, Japan, West America. 
Fossil, 1 sp. Miocene; Bordeaux. CC. CUhinensis, Chemn. 
(exiv, 33). 
Shell orbicular, somewhat convex, close; margins usually 
finely crenulated; beaks inclined anteriorly, no lunule; three 
small cardinal teeth, narrow, divergent and unequal; no lateral 
teeth ; two large muscular impressions, anterior oval, posterior 
semilunar; pallial impression short, the sinus deep and angular; 
ligament long and narrow. 
